Hydrogenation of high boiling oils



W. L- JACOBS! HYDROGENATION OF HIGH BOILING OILS Filed June 30, 1961 4REACTOR 5 5 H2 /0 i SEPARATOR 9\ V COMPRESSOR REACTOR COOLER 2/ COOLERSEPARATOR- ABSORBER 22 /9 1a 20 f v FUEL GAS SEPARATOR- M 29 17 /5 2a 23LIGHT H2O m WHYDROCARBONS W STRIPPER PURIFIED OIL RECYCLE H RYLE H20COOLED EFFLUENT OF REACTOR 9 SEPARATOR 2/ ABSORBER H20 To FROM INVENTORROBERT L. JACOBSO/V FIG. 2

United States Patent Oflice 3,145,160 Patented Aug. 18, 1964 Thisinvention relates to processes for hydrogen-treating hydrocarbon oils,and more particularly it relates to a catalytic hydrogenation processfor the removal of nitrogen compounds from high boiling oils in at leasttwo stages of contacting with sulfactive hydrogenation catalyst,including a last or second stage and a prior or first stage, withtreatment of the efiluents of the last stage and at least one priorstage.

By high boiling is meant those hydrocmbon fractions which remainsubstantially entirely in the liquid phase at reaction conditions.Specifically, the high boiling oils boil at least 90% above 600 F. andat least 10% above 750 F. It is particularly desired to provide aprocess for the removal of nitrogen compounds from oils boiling morethan 50% above 750 F. As examples of such oils may be mentioned reducedcrude, deasphalted residuum, heavy straight run gas oils, lube oils,waxes, heavy cracked cycle oils, coker gas oils, shale oil distillates,etc., and rafiinates or other components of such oils.

Several factors have a multiplying effect to make the removal ofnitrogen compounds from hydrocarbon oils by catalytic hydrogenationprogressively more difficult as feeds of increasingly higher boilingpoint are considered. Thus, the rate of hydrogenation of nitrogencompounds is slower with feeds of higher boiling point and with feeds ofhigher nitrogen content; and higher boiling feeds ordinarily containhigher concentrations of nitrogen com pounds. Hence, if a given lownitrogen content is desired in the product, more nitrogen compounds mustbe hydrogenated. Yet another factor is that the reaction by whichnitrogen compounds are converted to ammonia follows pseudo first orderreaction kinetics. Consequently, to convert for example 75% of thenitrogen content of an oil requires twice the catalyst volume orcontacting time as to convert 50% of the nitrogen.

The above factors all dictate the use of relatively more severeconditions when treating higher boiling oils for the removal of nitrogencompounds. Because there are practical limitations on the extent towhich the contacting time can be raised, the reaction rate must beincreased, for example by using a higher temperature. Because highertemperatures tend to increase the rate of coking and catalystdeactivation, a higher hydrogen partial pressure must be used tocounteract this effect. Unfortunately, the use of higher temperaturesalso tends to increase the production of light hydrocarbons byhydrocracking, thereby diluting the hydrogen and reducing the hydrogenpartial pressure.

The following comparative examples are presented to illustrate theeffects of feed boiling point and feed nitrogen content on the reactionrate.

Example I This example shows that low boiling oils are comparativelyeasily purified. A light cracked cycle oil boiling from 400 to 600 F.and containing 775 ppm. nitrogen was contacted with a sulfidedNi-Mo-alumina catalyst containing 5.6% Ni and 20.3% M at 590 F., 818p.s.i.g., and 1.0 LHSV, together with 4000 s.c.f. H per barrel of oil.After removal of NH the product was found to contain 25 ppm. N. Thus,96.8% of the nitrogen compounds was converted at these relatively mildconditions.

Example II This example shows that high boiling oils are quite difficultto purify. A heavy straight run gas oil having the following inspectionswas selected:

Gravity, API 21.9 Aniline point, F 149 Viscosity, SSU, at F 152 Sulfur,wt. percent 0.74 Nitrogen, total ppm 2,455 Distillation:

Start F 550 10% F 645 50% F 720 90% F 792 End F 850 This high boilingoil was contacted with a catalyst identical to that used in Example I at665 F., 1460 p.s.i.g., 0.76 LHSV, and 4000 s.c.f. H /bbl. The productcontained 500 p.p.m. N after removal of NH Thus, only 80% of thenitrogen was converted even though conditions were more severe than inExample 1.

Example III This example shows that the nitrogen content of the feed isan independent factor affecting the ease of purification. Anotherportion of the heavy gas oil feed of Example 11 was hydrogenated in afirst stage at a lower space velocity to reduce the nitrogen content toppm. This Nl-l -free material was then contacted in a second stage withthe 5.6% Ni-20.3% Mo sulfided catalyst at 650 F., 1500 p.s.i.g., 0.75LHSV, and 4000 s.c.f. H /bbl. The product contained 5 ppm. N afterremoval of NH Thus, 97% of the nitrogen was converted in the secondstage at a lower temperature than was used in Example ll. Over-all,99.8% of the nitrogen was removed.

Based on pseudo first order reaction kinetics, the above data show thatby removing 93% of the initial nitrogen content of the high boilingfeed, and the NH formed therefrom, the reaction rate of the remainingnitrogen compounds was increased more than two and one-half times, inExample Ill. Nevertheless, more severe operating conditions were stillrequired as compared to those used with the lower boiling feed ofExample I.

The present invention is based upon the concept of counteracting theinhibiting effect of the high nitrogen content of high boiling oils byremoving NH from the system, while at the same time increasing thehydrogen partial pressure by eliminating light hydrocarbons from thesystem. The invention comprises a process wherein a high boilinghydrocarbon oil is contacted in the liquid phase with a sulfactivehydrogenation catalyst in at least two stages, including a last stageand a prior stage. The process may be described as comprising eightsteps, as follows:

(1) Pass the oil and hydrogen-rich gas through a prior stage at elevatedtemperature and pressure,

(2) Separate the efiiuent of the prior stage into a liquid phase and avapor phase at substantially said elevated temperature and pressure,

(3) Pass the liquid phase through a last stage at elevated temperatureand pressure, with additional hydrogenrich gas,

(4-)Cool the vapor phase separated in step 2, to condense lighthydrocarbons therein, and remove NH; and the condensed lighthydrocarbons to obtain a clean vapor,

(5) Cool the entire effluent of the last stage (step 3), atsubstantially the elevated pressure used in said last stage, to obtain acooled liquid hydrocarbon efiiuent,

(6) Contact the clean vapor obtained in step 4 with the cooled liquidhydrocarbon efiluent obtained in step 5, at substantially the elevatedpressure of the last stage, to obtain a purified hydrogen-rich gas and aliquid hydrocarbon efiluent containing dissolved hydrocar' bons,

(7) Recycle the purified hydrogen-rich gas obtained in step 6 to atleast one stage, and

(8) Recover purified high boiling hydrocarbon oil from the liquidhydrocarbon effluent obtained in step 6.

Any number of stages in series may be used. Where a large volume of oilis to be purified, it will be convenient to use multiple parallel trainsof series stages. The detailed description herein is in terms of atwo-stage process, i.e., a last stage and a prior stage. Where there aremultiple prior stages, the effiuent of at least one is treated in themanner described. The effluents of other prior stages may be treated inthe same manner or in a conventional manner before passing to the nextstage. It is especially preferred to use the invention in conjunctionwith the final two stages, i.e., the last stage and the stage just priorto the last, because the greatest benefits are obtained from theinvention in removing the last traces of nitrogen compounds to producepurified oil having a very low nitrogen content.

In accordance with the invention, a high boiling hydrocarbon oil in theliquid phase and hydrogen-rich gas are passed at elevated temperatureand pressure through a prior stage containing a sulfactive hydrogenationcatalyst. For example, the raw feed may comprise a heavy gas oil boilingfrom about 650 F. to about 1100 F. and containing contaminating nitrogencompounds. In general, the temperature will be within the range 550850F., and the total pressure will be above 800 p.s.i.g. Preferredoperating conditions for such high boiling feeds are a temperature of650-750 F. at the inlet and a hydrogen partial pressure of 650-2500p.s.i.a. Hydrogen should be employed in a ratio of from about 1000 to10,000 standard cubic feet per barrel of oil, preferably about 3000 to5000 s.c.f./bbl. Under these conditions the high boiling oil ismaintained substantially in the liquid phase.

The catalyst generally comprises an alumina or silicaalumina supportcarrying one or more iron group metals and one or more metals of GroupVIB of the Periodic Table in the form of their oxides or sulfides.Typical catalyst metal combinations are cobalt-molybdenum,nickel-tungsten, nickel-molybdenum-tungsten, cobaltnickel-molybdenum,nickel-molybdenum, etc. Preferably, the catalyst comprises a highmetal-content, sulfided, nickel-molybdenum-alumina catalyst containing3l0% nickel and 12-30% molybdenum, especially 410% Ni and 15 .530% Mo.Such high metal-content sulfied catalysts are several times as active asthe conventional hydrofining catalysts for the hydrogenation of nitrogencompounds. The volume of catalyst employed is such that the liquidhourly space velocity is about 0.4-4 volumes of oil per hour per volumeof catalyst, preferably about 1 LHSV.

The efiluent of this prior stage consists of a liquid phase, comprisingpartially purified high boiling hydrocarbon oil containing a smallamount of dissolved gases, in equilibrium with a vapor phase, comprisinghydrogen, ammonia and other by-products', and vaporized lighthydrocarbons. The phases are separated at the elevated temperature andpressure of the prior stage. The liquid phase and added hydrogen-richgas are passed at elevated temperature and pressure through a laststage, also containing a sulfactive hydrogenation catalyst. Theoperating conditions in the last stage are in the same ranges as recitedabove for the prior stage, and the catalyst is of the same general type.

The effluent of the last stage consists of a liquid phase, comprisingpurified high boiling hydrocarbon oil containing a small amount ofdissolved gases, in equilibrium with a vapor phase, comprising hydrogen,ammonia and other by-products, and vaporized light hydrocarbons. Thisentire effluent is cooled, to near atmospheric temperature while stillat substantially the elevated pressure, to obtain a cooled liquidhydrocarbon efi luent, which dissolves nearly all of the ammonia andother by-products and light hydrocarbons in the system, and a cooledhydrogen-rich gas containing only a small amount of diluent gases. Theammonia may be removed separately, if desired, for example by waterwashing the eifluent.

The vapor phase separated from the efiiuent of the prior stage is alsocooled, to near atmospheric temperature while still at substantially theelevated pressure, whereby a major portion of the light hydrocarbonstherein condense to form a liquid hydrocarbon phase, containingsubstantial amounts of ammonia and other by-prodnets, in equilibriumwith a vapor phase, comprising hydrogen, undissolved ammonia and otherby-products, and uncondensed light hydrocarbons. The ammonia, andpreferably the other by-products, are removed from this vapor phase. Theresulting clean vapor, comprising hydrogen and uncondensed lighthydrocarbons, is contacted with the cooled liquid hydrocarbon efiluentof the last stage, whereby the uncondensed light hydrocarbons areabsorbed in said cooled liquid hydrocarbon efiluent, yielding a purifiedhydrogen-rich gas. This purified hydrogenrich gas is recycled to atleast one of the prior and last stages. Make-up hydrogen is continuouslyintroduced into the system to compensate for that consumed in thereactions. Ammonia and other by-products are removed from the contactedliquid hydrocarbon efiluent to recover purified high boiling hydrocarbonoil product.

By proceeding in the above manner it is found that the total catalystvolume required for accomplishing a given degree of purification of ahigh boiling oil is much less than would otherwise be required, becausethe reaction rate of nitrogen compounds in the last stage is severalfoldmore rapid than in the prior stage. Surprisingly, it is also found thatrates of hydrogenation of aromatics, particularly polynuclear aromatics,and of other color, gum, and coke precursors are also increased in thelast stage. Consequently, the invention provides improved processes forthe treatment of lube oils and for the production of high grade heatingoils. Lower temperatures may be employed in both stages than wouldotherwise be possible, thereby reducing the rate of catalystdeactivation as well as improving product quality.

A particular advantage of the process, however, is that it makesfeasible the complete removal of nitrogen compounds from much higherboiling oils than it was heretofore considered possible topurify, in aprocess having a long on-stream time. By complete removal is meant theconversion to ammonia of more than of the nitrogen initially containedin the oil. Preferably, more than 99% of the nitrogen is so removed. Itis especially desired to reduce the nitrogen content of the oils tobelow 10 ppm. (0.001 weight percent expressed as elemental nitrogen). Bya long on-stream time is meant that the time between catalystregenerations is sufiiciently long such that it is more economical toshut down the process and regenerate the catalyst than it would be toprovide stand-by or swing reactors for use while the deactivatedcatalyst in other reactors is being regenerated. More particularly, itis desired to provide a process wherein catalyst deactivation is so slowthat the process can be kept on-stream for at least 1000 hours withoutcatalyst regeneration. Using the preferred high metal content, sulfided,nickel-molybdenum-alumina catalysts in the process of this invention,that objective is attainable with all but the highest boiling and highlycontaminated oils. By eliminating light hydrocarbons from the system,this invention maintains a high hydrogen partial pressure without thenecessity of using an inordinately high total pressure to prevent rapidcatalyst deactivation. The high hydrogen partial pressure also increasesthe reaction rate of nitrogen compounds in high boiling oils.

Preferred modes of carrying out the invention are illustrated by theflow diagrams of the attached FIGURES l and 2. In these figures, onlythe most important equipment items are shown, the usual additional heatexchangers, furnaces, auxiliary piping, pressure control valves, etc.,not being shown, for simplicity.

In FIGURE 1, a high boiling hydrocarbon oil feed is introduced to theprocess through line I. Hydrogen-rich gas is added to the oil feedthrough line 2, and the combined streams pass through line 3 to reactor4. The oil and hydrogen are supplied at an elevated temperature near thetemperature employed in the reactor and at elevated pressure. Reactor 4contains a sulfactive hydrogenation catalyst in the form of one or morefixed beds of small pellets or particles. In reactor 4, the majorportion of the nitrogen compounds in the oil feed are hydrogenated toammonia. Thus, for example, if the oil initially contained about 2500p.p.m. nitrogen and it were desired to reduce this ultimately to aboutppm. nitrogen (99.6% removal), conditions in reactor 4 should be such asto reduce the nitrogen content to about 500 ppm. It will be noted thatalthough this represents a major portion of the nitrogen compounds beingremoved (80% actually it is only a minor portion of the over-all taskbecause of the nature of the denitrification reaction. To reduce thenitrogen content to 10 ppm. in a single stage would require the use of areactor from 3 to 4 times the size of reactor 4.

In addition to nitrogen compounds being hydrogenated to ammonia, sulfur,oxygen, and halogen compounds are hydrogenated to by-product gases, andvirtually all of the olefins and a portion of the aromatics in the feedare hydrogenated. Also, some or" the feed is hydrocracked to lighthydrocarbons, which are substantially in the vapor phase at the reactionconditions. When using the preferred high metal-content, sulfided,nickel-molybdenumalumina catalysts, the production of non-condensablehydrocarbons such as methane and ethane by hydrocracking is quite small.Most of the light hydrocarbons produced have 4 or more carbon atoms tothe molecule. The light hydrocarbons accumulate in the recycle gasstream in conventional processes until a high equilibrium concentrationis reached at which the net production will dissolve in the product oil.By the process of this invention the concentration of light hydrocarbonsin the system is greatly reduced because a large portion of suchmaterials is separately removed.

The etlluent of reactor 4 passes through line 5 to separator 6, whereinit is separated at the reactor temperature and pressure into two phases.The liquid phase comprises partially purified high boiling hydrocarbonoil containing only a small amount of dissolved light hydrocarbons andimpurities. The vapor phase comprises hydrogen, ammonia and otherby-products, such as H 8, H 0, etc., and vaporized light hydrocarbons,including low boiling components in the feed as well as those producedby hydrocracking reactions in reactor 4. The hydrocarbon oil phaseseparated in separator 6 flows by gravity or pressure differential,still at substantially reactor temperature, through line 7 to reactor 9.Hydrogen-rich gas is also introduced through line 8. Instead ofproviding separate reactor vessels and an external phase separator,reactor 4 may represent an upper bed and reactor 9 a lower bed within asingle vessel, and separator 6 may be a vaporsealed distributor traybetween the beds.

Reactor 9 is preferably similar in all respects to reactor 4 althoughthe pressure will be somewhat lower due to pressure drop through thesystem. It is found that the total quantity of catalyst required inreactors 4 and 9 is slightly less if reactor 9 is made somewhat smallerthan reactor 4. Nevertheless, the savings is so small (usually under10%) that, for convenience in fabrication, it is usually preferable tomake the reactors the same size. Also, the optimum manner ofdistributing the catalyst between reactors 4 and 9 depends on the degreeof nitrogen removal desired, and the greater the degree of purificationdesired, the more nearly equal the reactors should be.

Since most of the olefins and other hydrocarbons having a tendency todeactivate catalysts by forming coke have been hydrogenated in reactor4, it will be found that a somewhat higher temperature may be used inreactor 9 without causing increased catalyst fouling. For example, thetemperature may be increased 550 F, depending on the nature of the feedand the conditions in reactor 4. In all cases it is found that, byvirtue of excluding from reactor 9 the ammonia, other byproducts, andlight hydrocarbons contained in the vapor phase eflluent of reactor 4 amuch higher rate of conversion of nitrogen compounds to ammonia isrealized in reactor 9 even at the same temperature. For example, when ofthe initial nitrogen is converted in reactor 4 (nitrogen content reducedfrom 2500 to 500 ppm), 98% of the remaining nitrogen is converted inreactor 9 at the same temperature and space velocity (to 10 ppm.residual). Moreover, as previously mentioned, the rate of hydrogenationof other contaminants and of aromatics is higher in the last stage,reactor 9.

The vapor phase from separator 6, still at. substantially thetemperature and pressure of reactor 4, is withdrawn through line 10 andthen cooled, as in heat exchanger 11, to condense a major portion of thelight hydrocarbons therein. Preferably, the temperature is reduced tonear atmospheric conditions, in any case below F. The condensed lighthydrocarbons and non-condensable vapors then continue through line 12 toseparator 15 wherein the condensed light hydrocarbons separate as aliquid oil phase from the uncondensed vapors while still atsubstantially reactor pressure. The condensed light hydrocarbonsdissolve much of the ammonia and other byproducts, but the Vapor phasein equilibrium therewith also contains ammonia as well as uncondensedlight hydrocarbons. The ammonia is to be removed from this vapor phasein accordance with the invention. Preferably, this is accomplished byinjecting liquid water through line 13 with provisions for intimatecontacting, such as mixing valve M. In that case, a three-phase systemis formed in separator 15 comprising a liquid water phase, containing insolution nearly all of the ammonia in the system, a liquid lighthydrocarbon oil phase, containing in solution ammonia, other by-productsand normally gaseous hydrocarbons, and a vapor phase, comprisinghydrogen, uncondensed light hydrocarbons, and only a small amount ofammonia and other byproducts. The liquid Water phase is withdrawn fromthe system through line 116; the liquid hydrocarbon phase is withdrawnthrough line 17; and the vapor phase is withdrawn from separator 15through line 118. Alternately, or in addition, ammonia and otherby-products may be removed from the cooled vapor phase by other means,such as by adsorption on a solid contact agent, such as silica-aluminabeads, molecular sieves, etc.

In reactor 9, the desired conversion of nitrogen compounds to ammonia iscompleted, other impurities are converted to gaseous by-products, somefurther hydrogenation of aromatics occurs, and some furtherhydrocracking of the high boiling oil to light hydrocarbons occurs. Theefiluent of reactor 9 is withdrawn through line 19. At this point theefiiuent consists of a liquid phase, comprising purified high boilingliquid hydrocarbon oil containing only a small amount of dissolved lighthydrocarbons and impurities, and a vapor phase comprising hydrogen,ammonia and other by-products, and vaporized light hydrocarbons. Thisefliuent is cooled, as in heat exchanger 20, to condense the lighthydrocarbons at substantially reactor pressure. Preferably, the effluentis cooled to near atmospheric temperature, in any case below 150 F. Theeilluent continues through line 21 to separator-absorber 22. In line 21the system consists of a high boiling liquid hydrocarbon oil phase,having dissolved therein most of the ammonia produced in reactor 9 andnearly all of the light hydrocarbons, in equilibrium with a vapor phase,comprising hydrogen, a minor amount of am monia and other by-products,and a minor amount of uncondensed light hydrocarbons. These phasesseparate in the upper portion of separator-absorber 22. The vapor phasepasses out through line 24. The oil phase passes downward,countercurrent to the upilowing cooled vapor stream introduced at thebottom through line 18, and continues out of the multiple stage absorbervia line 23. In the absorber section of separator-absorber 22 theuncondensed light hydrocarbons in the stream in line 18 are absorbed inthe high boiling hydrocarbon oil because the oil is higher boiling thanthat separated in separator 15 and because there is a much largerquantity of high boiling oil to absorb the light hydrocarbons. Also,since most of the light hydrocarbons produced in reactor 4 are withdrawnthrough line 17, the high boiling oil has a greater capacity to dissolvethe remaining portion than would otherwise be the case. A hydrogen-richgas stream is thereby produced which passes up through separatorabsorber22 and commingles with the vapor phase separated from the cooledeffiuent of reactor 9 to provide a hydrogen-rich recycle gas in line 24.The combined hydrogen-rich gases are returned through lines 2 and 8 toreactors 4 and 9 by means of recycle gas compressor 25. Make-up hydrogenis added to the system to compensate for that consumed in the reactions.Preferably, the make-up hydrogen, if of high purity, is added throughline 26 to line 8 in order that the hydrogen to reactor 9 will beslightly more pure than that to reactor 4.

It is within the contemplation of this invention to inject stream 18directly into stream 211, in effect reducing to one the number of traysin separator-absorber 22. Water may also be injected into the separatorto assist in removal of NH produced in reactor 9.

The liquid high boiling hydrocarbon oil in line 23 passes to stripper28, which operates at a materially lower pressure, as signified by valve27. Ammonia and other byproducts are taken overhead through line 29 anddisposed of, for example, as fuel gas. The purified high boilinghydrocarbon oil product is withdrawn through line 30. The lighthydrocarbons may also be separately recovered using stripper 28, ifdesired.

FIGURE 2 illustrates another manner of effecting separation of thecooled liquid hydrocarbon oil effluent of the second reactor for contactwith the vapor phase separated after cooling and removing lighthydrocarbons and ammonia from the vapor phase efliuent of the firstreactor. Separator-absorber 22 of FIGURE 1 is divided into two separatevessels, whereby the ammonia and light hydrocarbon content of the recylegas is further reduced. As shown in FIGURE 2, the cooled effluent ofreactor 9 in line 21 passes to separator 32. Liquid water is injectedthrough line 31 such that in separator 32 a three-phase system is formedconsisting of a liquid water phase, containing the ammonia and otherby-products produced in reactor 9 a liquid oil phase comprising highboiling hydrocarbon oil and dissolved light hydrocarbons, and a vaporphase, comprising hydrogen-rich gas containing only minor amounts ofammonia and other by-products. The hydrogen-rich gas is withdrawnthrough line 34 and recycled to the reactors, as before. The liquidwater phase is disposed of through line 33. The liquid hydrocarbon oilphase is withdrawn through line 35 to absorber 36 wherein it passesdownward countercurrent to the upflowing vapors from separator 15introduced through line 18. The hydrocarbon oil thereby absorbs thelight hydrocarbons contained in stream 18, and the oil is then passedthrough line 23, as before, to the stripper. Hydrogen-rich gas therebyproduced is withdrawn overhead through line 37 and recycled to thereactors separately or in combination with stream 34.

I claim:

1. A process for the removal of nitrogen compounds initially containedin a high boiling hydrocarbon oil boiling at least above 600 F. and atleast 10% above 750 F. in at least two stages of contacting withsulfactive hydrogenation catalyst, including a second stage and a firststage, which process comprises the steps:

(1) passing high boiling hydrocarbon oil in the liquid phase andhydrogen-rich gas through a first stage at elevated temperature andpressure to convert a major portion of the nitrogen compounds initiallycontained in said oil to ammonia,

(2) separating the efiluent from step (1) into a liquid phase and avapor phase at substantially said elevated temperature and pressure,

(3) passing hydrogen-rich gas and said liquid phase separated in step(2) through a second stage at elevated temperature and pressure, toconvert a major portion of the remaining nitrogen compounds to ammonia,

(4) cooling said vapor phase separated in step (2) and removing ammoniaand condensed light hydrocarbons therefrom to obtain a clean vaporcomprising hydrogen and uncondensed light hydrocarbons,

(5) cooling the entire effluent from step (3) at substantially saidelevated pressure to obtain a cooled liquid hydrocarbon effluent,

(6) contacting the clean vapor from step (4) with the cooled liquidhydrocarbon efliuent from step (5) at substantially said elevatedpressure to absorb light hydrocarbons from said clean vapor in saidcooled effluent and thereby obtain a purified hydrogen-rich gas and aliquid hydrocarbon efiluent containing dissolved light hydrocarbons,

(7) recycling said purified hydrogen-rich gas from step (6) to at leastone stage, and

(8) recovering purified high boiling hydrocarbon oil from the liquidhydrocarbon effluent from step (6).

2. The process of claim 1 wherein said clean vapor from step (4) iscontacted with said cooled liquid hydrocarbon efiiuent in step (6) byadmixing said clean vapor with the entire cooled eflluent of step (5),and in step (7) said hydrogen-rich gas is recycled to both said laststage and said prior stage.

3. The process of claim 1 wherein ammonia is removed from the vaporphase separated in step (2) by cooling said vapor, adding water thereto,and separating water containing dissolved NH from the clean vapor.

4. The process of claim 1 wherein said sulfactive hydrogenation catalystcomprises a high metal-content, sulfided, nickel-molybdenum-aluminacatalyst containing 310% nickel and 12-30% molybdenum.

5. The process of claim 1 wherein more than 90% of the nitrogeninitially contained in said oil is converted to ammonia.

6. The process of claim 4 wherein the process is kept on-stream for atleast 1000 hours without catalyst regen- 'eration.

7. The process of claim 1 wherein said high boiling hydrocarbon oilboils at least 50% above 750 F.

8. The process of claim 1 wherein said high boiling hydrocarbon oil is alube oil.

References Cited in the file of this patent UNITED STATES PATENTS2,760,907 Attane et al Aug. 28, 1956 2,840,513 Nathan June 24, 19582,937,134 Bowles May 17, 1960 3,071,542 Davis et a1. Jan. 1, 1963

1. A PROCESS FOR THE REMOVAL OF NITROGEN COMPOUNDS INITIALLY CONTAINEDIN A HIGH BOILING HYDROCARBON OIL BOILING AT LEAST 90% ABOVE 600*F. ANDAT LEAST 10% ABOVE 750*F. IN AT LEAST TWO STAGES OF CONTACTING WITHSULFACTIVE HYDROGENATION CATALYST, INCLUDING A SECOND STAGE AND A FIRSTSTAGE, WHICH PROCESS COMPRISES THE STEPS: (1) PASSING HIGH BOILINGHYDROCARBON OIL IN THE LIQUID PHASE AND HYDROGEN-RICH GAS THROUGH AFIRST STAGE AT ELEVATED TEMPERATURE AND PRESSURE TO CONVERT A MAJORPORTION OF THE NITROGEN COMPOUNDS INITIALLY CONTAINED IN SAID OIL TOAMMONIA, (2) SEPARATING THE EFFLUENT FROM STEP (1) INTO A LIQUID PHASEAND A VAPOR PHASE AT SUBSTANITALLY SAID ELEVATED TEMPERATURE ANDPRESSURE, (3) PASSING HYDROGEN-RICH GAS AND SAID LIQUID PHASE SEPARATEDIN STEP (2) THROUGH A SECOND STAGE AT ELEVATED TEMPERATURE AND PRESSURE,TO CONVERT A MAJOR PORTION OF THE REMAINING NITROGEN COMPOUNDS TOAMMONIA, (4) COOLING SAID VAPOR PHASE SEPARATED IN STEP (2) AND REMOVINGAMMONIA AND CONDENSED LIGHT HYDRO/ CARBONS THEREFROM TO OBTAIN A CLEANVAPOR COMPRISING HYDROGEN AND UNCONDENSED LIGHT HYDROCARBONS. (5)COOLING THE ENTIRE EFFLUENT FROM STEP (3) AT SUBSTANTIALLY SAID ELEVATEDPRESSURE TO OBTAIN A COOLED LIQUID HYDROCARBON EFFLUENT, (6) CONTACTINGTHE CLEAN VAPOR FROM STEP (4) WITH THE COOLED LIQUID HYDROCARBONEFFLUENT FROM STEP (5) AT SUBSTANTIALLY SAID ELEVATED PRESSURE TO ABSORBLIGHT HYDROCARBONS FROM SAID CLEAN VAPOR IN SAID COOLED EFFLUENT ANDTHEREBY OBTAIN A PURIFIED HYDROGEN-RICH GAS AND A LIQUID HYDROCARBONEFFLUENT CONTAINING DISSOLVED LIGHT HYDROCARBONS, (7) RECYCLING SAIDPURIFIED HYDROGEN-RICH GAS FROM STEP (6) TO AT LEAST ONE STAGE, AND (8)RECOVERING PURIFIED HIGH BOILING HYDROCARBON OIL FROM THE LIQUIDHYDROCARBON EFFLUENT FROM STEP (6).